● For effective treatment of a disease, early `color{violet}("diagnosis")` and understanding its
`color{violet}("pathophysiology")` is very important.

● Using conventional methods of `color{violet}("diagnosis (serum and urine analysis, etc.)")` early detection is not possible.

● `color{violet}("Recombinant DNA")` technology, Polymerase Chain Reaction (PCR) and
`color{violet}("Enzyme Linked Immuno-sorbent Assay (ELISA)")` are some of the techniques that serve the purpose of early
`color{violet}("diagnosis")`.

● Presence of a `color{violet}("pathogen (bacteria, viruses, etc.)")` is normally suspected only when the
`color{violet}("pathogen")` has produced a `color{violet}("disease symptom")`.

● By this time the concentration of `color{violet}("pathogen")` is already very high in the body.

● However, very low concentration of a `color{violet}("bacteria or virus")` (at a time when the symptoms of the disease are not yet visible) can be detected by `color{violet}("amplification")` of their `color{violet}("nucleic acid by PCR")`.

● `color{violet}("PCR")` is now routinely used to detect `color{violet}("HIV")` in suspected `color{violet}("AIDS")` patients.

● It is being used to detect `color{violet}("mutations")` in genes in suspected `color{violet}("cancer patients")` too.

● It is a powerful techqnique to identify many other `color{violet}("genetic disorders")`.

● A single stranded `color{violet}("DNA or RNA")`, tagged with a `color{violet}("radioactive molecule (probe)")` is allowed to
`color{violet}("hybridise")` to its `color{violet}("complementary DNA")` in a `color{violet}("clone of cells")` followed by detection using `color{violet}("autoradiography")`.

● The `color{violet}("clone")` having the mutated gene will hence not appear on the `color{violet}("photographic film")`,
because the probe will not have complementarity with the `color{violet}("mutated gene")`.

● `color{violet}("ELISA")` is based on the principle of `color{violet}("antigen-antibody interaction")`.

● Infection by `color{violet}("pathogen")` can be detected by the
`color{violet}("presence of antigens (proteins, glycoproteins, etc.)")` or by detecting the `color{violet}("antibodies synthesized against the pathogen")`.

● Animals that have had their `color{violet}("DNA")` manipulated to `color{violet}("possess and express an extra (foreign) gene")` are known as `color{violet}("transgenic animals")`.

● `color{violet}("Transgenic rats, rabbits, pigs, sheep, cows and fish")` have been produced, although over
`color{violet}("95 percent")` of all existing `color{violet}("transgenic animals are mice")`.

● `color{green}("THEIR ADVANTAGES:")`

`star` `color{brown}("Normal physiology and development:")`

● `color{violet}("Transgenic animals")` can be specifically designed to allow the study of how
`color{violet}("genes")` are regulated, and how they affect the normal functions of the body and its development, e.g., study of complex factors involved in growth such as `color{violet}("insulin-like growth factor")`.

● By introducing `color{violet}("genes")` from other species that alter the formation of this factor and studying the biological effects that result, information is obtained about the `color{violet}("biological role of the factor in the body")`.

`star` `color{brown}("Study of disease:")`

● Many `color{violet}("transgenic animals")` are `color{violet}("designed to increase")` our understanding of how
`color{violet}("genes")` contribute to the development of `color{violet}("disease")`.

● These are specially made to serve as models for `color{violet}("human diseases")` so that investigation of new
`color{violet}("treatments")` for `color{violet}("diseases is made possible")`.

● Today `color{violet}("transgenic models exist")` for many `color{violet}("human diseases")` such as
`color{violet}("cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s")`.

`star` `color{brown}("Biological products:")`

● `color{violet}("Medicines")` required to treat certain `color{violet}("human diseases")` can contain biological products, but such products are often expensive to make.

● `color{violet}("Transgenic animals")` that produce useful `color{violet}("biological products")` can be created by the introduction of the `color{violet}("portion")` of `color{violet}("DNA (or genes)")` which codes for a particular product such as
`color{violet}("human protein (α-1-antitrypsin) ")` used to `color{violet}("treat emphysema.")`

● Similar attempts are being made for `color{violet}("treatment of phenylketonuria (PKU)")` and `color{violet}("cystic fibrosis")`.

● `color{violet}("In 1997")`, the first `color{violet}("transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre)")`.

● The milk contained the `color{violet}("human alpha-lactalbumin")` and was nutritionally a more balanced product for
`color{violet}("human babies")` than natural `color{violet}("cow-milk.")`

` star` `color{brown}("Vaccine safety")`

● `color{violet}("Transgenic mice")` are being developed for use in testing the safety of
`color{violet}("vaccines")` before they are used on `color{violet}("humans")`.

● `color{violet}("Transgenic mice")` are being used to test the safety of the `color{violet}("polio vaccine")`.

● If successful and found to be reliable, they could replace the use of `color{violet}("monkeys")` to test the safety of batches of the vaccine.

`star` `color{brown}("Chemical safety testing")`
● This is known as `color{violet}("toxicity/safety testing")`.

● The procedure is the same as that used for `color{violet}("testing toxicity of drugs")`.

● `color{violet}("Transgenic animals")` are made that
`color{violet}("carry genes")` which make them more `color{violet}("sensitive to toxic")` substances than
`color{violet}("non-transgenic animals")`.

● They are then exposed to the `color{violet}("toxic substances")` and the effects studied.

● `color{violet}("Toxicity testing")` in such animals will allow us to obtain results in less time.